jagwap
1000+ Head-Fier
Because Head-fi
Amps that are designed to be used in balanced mode are almost always going to sound different, usually worse, in single-ended mode. It has nothing to do with that they are balanced vs. all amps out there that aren't, but because the amp is designed to be used with the balanced output. By using a balanced amp from the single-ended output, you're not using half the circuit. It would not be unlike if I removed half the circuit in my non-balanced amp then had a listen -- it would likely sound worse too. You could build a balanced CMOY for your HD800s (or the HD800S) if you wanted (it has been done) and I don't think it would sound any better than much other than a regular CMOY.
When an amp designer makes an amp, a balanced circuit is just one of many design choices, alongside whether to use negative feedback, tubes, a hybrid circuit or any other such thing. The reason that balanced designs get a lot of attention, secondly only to tube amps, is because we have to use a different cable with our headphones, in this case, Sennheiser are offering their own cable, which I don't know to be any different to the regular cable than the different plug on the end.
This is not necessarily true. A well designed single ended amplifier will still benefit from being made balanced if it is well designed.